This invention relates to a radio communication apparatus which has a plurality of input terminals supplied with a plurality of input baseband signals.
A radio communication apparatus of the type described, comprises a transmitting portion which is connected to the input terminals. The transmitting portion selectively transmits the input baseband signals in response to a selection signal.
As will later be described, a transmitting portion of a conventional radio communication apparatus comprises a plurality of level controllers which have a plurality of fixed gains, respectively, and which are connected to the input terminals, respectively. Each of the level controllers controls the input baseband signal in question so that the input baseband signal has an optimum level.
A plurality of switches are connected to the level controllers, respectively. Each of the switches produces, as an output signal thereof, the input baseband signal only when the switch under consideration is put into an on state. Responsive to the selection signal, a switch controller controls the switches to put one of the switches into the on state. This one of the switches corresponds to the baseband input signal which is indicated by the selection signal. Connected to the switches, an adder adds output signals of the switches together and produces an added signal.
A baseband processor carries out a baseband processing of the added signal to produce a processed signal. For example, the baseband processor carries out a band restriction processing of the added signal, namely, a band-pass filtering processing of the added signal. A modulator modulates the processed signal into a modulated signal. A radio frequency amplifier amplifies the modulated signal as a radio signal which is transmitted from an antenna.
With this structure, the level controller must deal with each of the input baseband signals. Therefore, the number of the level controllers increases as the number of the input baseband signals increases.